The invention generally relates to multipurpose pumps useful for various applications, such as oil well servicing, oil well stimulation, water blasting, and various industrial uses. The invention is more specifically directed to the mounting of a fluid cylinder to the power end assembly of a pump.
The prior art techniques for mounting a fluid cylinder to a pump require the machining of flanges in the fluid cylinder block in order to create nut pockets for affixing nuts to the threaded ends of stay rods passing through the flanges. The creation of these flanges requires extensive machining time and further demands the accurate alignment of through bores cut through the flanges for passages of stay rods to be affixed thereto and aligned axially with corresponding bores in the pump frame. At the opposite ends of the stay rods, threaded portions threadingly engage the threaded bores of the pump frame.
Typically, pumps of the kind primarily envisioned for the present invention are high pressure devices, often reaching pressures in the range of 10-20,000 psi (703 Kg/cm2-1406 Kg/cm2). Such are often used as oil stimulation pumps well known in the petroleum industry. In these arrangements, pony rods driven by crank shaft drives within the pump""s power end assembly are drivingly cooperative with reciprocating plungers communicating within the fluid cylinder for providing high pressure fluid discharge. High stresses can be created with pumps operating normally in the range of 350-2000 BHP for driving plungers that are typically from about 4xe2x80x3 to 8xe2x80x3 in diameter.
Normally, each pony rod and an associated plunger have four stay rod assemblies therearound for interconnecting the frame of the pump to machined flanged portions of the fluid cylinder block. The machining required to create the flanged portions inherently eliminates valuable stabilizing mass and strength from the block of steel forming the fluid cylinder. Zones of weakness are created by this procedure. Machining the steel block also requires a significant amount of labor cost and time. Built in to the machining process is potential stay rod alignment inaccuracy by cutting bores in the flanges for accommodating the stay rods and forming nut pockets for fastening the rods to the flanges. This prior art method can also affect the alignment of the pony rods and plungers. With the high pressures developed by the pumps and resultant dynamic forces, coupled with the concurrent rapid reciprocation times of the pony rods, even slight misalignments can cause early machine part wear, breakdowns, loss of power, and the requirement to check and retighten connections.
It is therefore a goal of the present invention to eliminate the expensive and strength reducing process of forming flanges and nut pockets in a fluid cylinder block. Because of the special performance requirements of high pressure pumps, the fluid cylinder blocks are not cast but are forged from special heat treated steels. Accordingly, it is an adjunct goal of the invention to maintain the full stabilizing mass of the forged fluid cylinder block for retaining strength, eliminating weakened zones, and maximizing pump-to-fluid cylinder pony rod/plunger alignments.
It is a concomitant object of the invention to eliminate the prior art techniques of creating weakened flange sections which have been required to be made in order to provide through-bores necessary to connect nuts to the stay rods extending therethrough from the pump frame.
It is an allied objective of the invention to provide for a direct attachment to the fluid cylinder block internally of the steel mass forming the fluid cylinder block.
The invention replaces the bolted stay rod technique of the prior art and provides a unique tie rod and exteriorly threaded connector assembly to clampingly embed the tie rods directly into the steel block forming the fluid cylinder and co-axially aligning them with corresponding engageable bores in the pump frame.
A plurality of tie rods are provided with either a short or long sleeve-like threaded connector for attachment to the fluid cylinder block. The short and long connectors facilitate a captive and anchored clamping of shouldered heads of the tie rods within at least partially threaded bores in the fluid cylinder block. Usually with multiple pump pony rods, each pony rod is associated with a fluid cylinder plunger and four tie rods and connectors. The short and long connectors preferably are arranged, respectively, at upper and lower adjacent tie rods to permit for the direct passage of a tightening wrench to reach and facilely engage a hex head of a connector at the correct 90xc2x0 relation for accurate threading rotation for clamping the tie rod to the fluid cylinder. The opposite end of the tie rod is threaded and forms a shoulder relief portion for accommodating a pump frame spacer, which spacer is pressed against the pump frame as the threaded end of the tie rod threadingly engages a threaded bore in the pump frame. A grippable surface of the tie rod is created along the tie rod, such as by knurling, to facilitate the sure grip of a pipe wrench for tightening to the pump frame. Optionally, the shouldered head of the tie rod is provided with an axial hex bore, which facilitates the initial starting of the threaded connection at the other end to the pump frame, such as by means of a drill and bit spinning the tie rod, leaving only the final tightening of the threaded engagement to the pump frame by, for example, a torque wrench gripping the knurled surface.
The shouldered head of the tie rod has an abuttable annular shoulder surface forcefully contacted by a short or long connector as the connector is tightened into a fluid cylinder threaded bore, thereby inserting and clamping the shouldered head into the bore of the fluid cylinder. The leading, or terminal, end of the shouldered head is preferably provided with a circumferential chamfer, which bottoms out generally at the drill point bottom wall of the threaded bore.
In a standard configuration for an oil well stimulation pump, three pony rods driven by the pump power end assembly are drivingly associated with three fluid cylinder plungers. The invention provides a method for the quick connection of twelve tie rods (four tie rods around each plunger), having sleeve-like short or long connectors slidingly placed thereon, which tie rods are subsequently rotated by means of a power drill, or the like, engaging the hex end bores of the tie rods and spinning them for preliminary attachment of the opposite threaded ends to twelve threaded bores in the pump frame. The tie rods are then finally tightened by means of a torque wrench or the like. The fluid cylinder is then brought adjacent to the power end assembly of the pump having the attached tie rods, and the tie rod shouldered heads are inserted into twelve threaded bores in the fluid cylinder block. The connectors are then wrench-tightened at hex bolt heads thereof to force the connectors against the shouldered heads and embeddingly clamp the tie rods inside the bores to thereby securely mount the fluid cylinder on the pump frame.